The health and conditions of cores of nuclear reactors used in nuclear power plants or other applications are critical to public safety and reliable operation of the nuclear reactors. However, it is technically challenging to provide effective monitoring or inspecting systems to monitor the conditions of the inner core of a nuclear reactor through the reactor enclosure and protective mechanisms.
The 9.0-magnitude earthquake followed by a tsunami in March of 2011 caused an ongoing nuclear crisis at Fukushima Daiichi in Japan. Failure of the Fukushima Daiichi reactors is attracting world-wide attention to the issue of the fundamental safety of atomic energy. In spite of the intense effort by Tokyo Electric Power Company (TEPCO) and the Japanese government, the three reactors, units #1, #2 and #3 appear to have some level of melting down. Though the reactors are gradually stabilizing, the detection of Xe from Reactor #2 suggests there is a small but undeniable possibility of re-criticality. The recovery and decommissioning process for a reactor can be unpredictable without some realistic estimation of the amount and location of the melted fuel and the extent of the damage to the reactor. In the 1979 nuclear power plant accident at Three Miles Island in Dauphin County, Pennsylvania, it took more than 3 years before a “quick look” camera could be put into the reactor, and about 10 years before the total damage to the reactor could be assessed.